Source: NBER Derived Data By Dividing Series (Loaded Wagon-Miles) By Series (Total Wagon-Miles)
This NBER data series q03076 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: q03076
Release: NBER Macrohistory Database
National Bureau of Economic Research, Ratio of Loaded Wagon-Miles To Total Wagon-Miles for Great Britain [Q03076GBQ501NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/Q03076GBQ501NNBR/, October 6, 2015.